In the general industrial machinery fields, a mechanical-system control element is driven by an electric motor. However, in recent years, there have been proposed and developed various mechanically and electrically integrated electromotive drive devices, in which an electronic control unit that is configured to control a rotational speed and a rotational torque of an electric motor and comprised of semiconductor elements or the like, is integrally incorporated in the electric motor.
For instance in an automotive electric power steering device exemplified as a mechanically and electrically integrated electromotive drive device, both of a rotational direction and a rotational torque of a steering shaft, which is rotated by operating a steering wheel by the driver, are detected. The automotive electric power steering device is configured to drive the electric motor so as to rotate the steering shaft in the same direction as the rotational direction of the steering shaft on the basis of the detected values, thereby generating a steering assist torque.
Generally, the automotive electric power steering device uses a three-phase alternating-current brushless electric motor as an electric actuator. To drive and control the electric motor, an electronic control unit (a controller) including power-system electronic components is required. However, in recent years, to simplify the configuration, generally, the electronic control unit is not mounted separately from the electric motor, but integrated with the electric motor.
As an example of an electric motor (an electromotive drive device) for use in an electric power steering device, for instance, Japanese patent provisional publication No. JP2013-090532 A (Patent document 1) discloses an electronic control unit having a control circuit board equipped with control-system electronic components that include a microprocessor, and a power-conversion circuit board equipped with power-system electronic components that constitute an inverter. The control circuit board and the power-conversion circuit board are arranged one above the other inside of the housing provided at one end of the electric motor. In the device of the Patent document 1, a magnetic rotation sensor, which is combined with a magnet part located at a rotation shaft end, is used as a sensor for detecting rotation of the electric motor. The rotation sensor, which has a comparatively small package, is installed on a surface of the control circuit board, in more detail, on the surface of the control circuit board facing the rotation shaft end of the electric motor.